The invention relates generally to control of work machines and, more particularly, to a method and apparatus for determining the location and orientation of a work implement in response to an external reference.
Work machines such as excavators, backhoes, front shovels, and the like are used for excavation work. These excavating machines have work implements which consist of boom, stick and bucket linkages. The boom is pivotally attached to the excavating machine at one end, and its other end is pivotally attached to a stick. The bucket is pivotally attached to the free end of the stick. Each work implement linkage is controllably actuated by at least one hydraulic cylinder for movement in a vertical plane. An operator typically manipulates the work implement to perform a sequence of distinct functions which constitute a complete excavation work cycle.
The earthmoving industry has an increasing desire to automate the work cycle of excavating machines for several reasons. Unlike a human operator, an automated excavating machine remains consistently productive regardless of environmental conditions and prolonged work hours. The automated excavating machine is ideal for applications where conditions are dangerous, unsuitable or undesirable for humans. An automated machine also enables more accurate excavation making up for any lack of operator skill.
Much effort has gone into developing the automatic excavation algorithms. For example, the digging and therefore the bucket position may be described relative to the excavator car body or house. As long as the house sits horizontally on the ground (no tilt or pitch), the computations can be made to determine the bucket location provided that the house location is known. As the orientation of the excavator changes, additional sensors are added to determine the pitch and roll to compensate. Often a laser system is used to determine the elevation of the body and multiple detectors on the house are used to determine orientation.
Alternatively, x, y, and z location, as well as roll and pitch information, for a work machine may be determined using a single sensor. For example, see U.S. Pat. No. 5,438,771, entitled xe2x80x9cMethod and Apparatus for Determining the Location and Orientation of a Work Machine.xe2x80x9d In this method, the car body is rotated. Signals are received from an external reference source. The x, y, and z location of a receiver is determined as the car body rotates, based on the location of the receiver at a plurality of points during the rotation. From this information, the location and orientation of the car body can be determined.
The above method requires that at least three location points be obtained. The first point is measured at the start of a reversal of swing. The second point is measured at a valid point a certain distance from the first point. The third point is measured at the endpoint of an arc, signaled by another reversal of swing. Most importantly, however, the method requires that the machine does not tram (or move) and rotate at the same time. In this situation, the location and orientation information determined by the processor is invalidated.
This invalidation presents a problem for mining operations. When this happens, the system may be unable to determine the material composition of the bucket load. In a typical mining situation, this may result in up to 20% of bucket loads being unidentified. This may result in sending ore to a waste site and/or sending waste to an ore processing site. Further, this situation limits the ability to automate an excavation process.
The present invention is directed to overcoming one or more of the problems or disadvantages associated with the prior art.
A method is provided for determining the location of a work machine at a work site, where the work machine includes a house, a boom connected to the house, a stick connected to the boom, and a work implement connected to the stick. Reference signals are received from an external reference source. The position of a point on the house is determined in response to the received signals. Information about the work machine is determined based on the position of a point on the house. The status of center-of-rotation (COR) information is updated. The system determines if an event has occurred. If an event is determined to have occurred, event reactions occur.
An apparatus is provided for determining the location of a work machine at a work site. The apparatus comprises a house, a boom connected to the house, a stick connected to the boom, and a work implement connected to the stick. The apparatus further includes a positioning system including a receiver connected to the house. The positioning system is configured to determine the location of the receiver in three dimensional space at a plurality of points as the house is rotated and further to determine the location and orientation of the work implement in response to the location of the plurality of points. The apparatus also includes a sensor configured to identify an event and a processor configured to determine the location of the receiver in three dimensional space at the time of an event and to process the event in relation to the location of the receiver and the location of the plurality of points.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed.